1. The Field of the Invention
The application is directed to compositions and methods for forming dental compositions. More particularly, the compositions and methods are directed to dental compositions which have adhesive, antimicrobial and/or reparative dentin stimulating properties. These compositions are primarily useful as pulp caps and liners.
2. The Relevant Technology
Conventional dentin liners and pulp caps provide several advantageous properties which make these dentin liners and pulp caps useful in restorative dentistry. However, these useful properties cannot be reliably obtained.
Conventional dental liners are used to line a preparation made in a tooth after a cavity has been excavated in order to receive a filling material, particularly when the preparation penetrates beyond the enamel and deeply into the dentin. Dental liners are utilized before application of a filling material to act as a barrier against ingress of bacteria which can cause decay, to stimulate reparative dentin and/or to provide thermal insulation.
Dental liners can be used with any type of filling material; although, bonded composite fillings typically form a relatively solid seal so it is generally not necessary to use dental liners with composite fillings unless the preparation extends into a pulpal exposure or is near a pulpal exposure. Dental liners are, however, generally needed with metal amalgam fillings since metal amalgam fillings typically fail to seal the exposed interior of the tooth from accessibility by bacteria, to stimulate reparative dentin and/or to provide thermal insulation.
The same dental material utilized for liners is also conventionally utilized for pulp capping to protect the pulp after excavating deep caries which result in penetration near or into the pulp chamber. The pulp and the adjacent tissue, the pink dentin, are the living portion of a tooth and accordingly are highly sensitive. A failure to properly seal the pulp chamber can potentiate bacteria to infect the pulp. Since the infected area is in a hard and rigid tooth, the infected area cannot expand with the inflammation caused by the infection which causes the blood flow to the infected area to be restricted. As a result of the blood supply being restricted, the ability of the pulp to fight off the infection is compromised which generally causes the tooth to die. Accordingly, it is crucial to protect the pulp from infection by utilizing a pulp cap as a barrier against ingress of bacteria and/or to initiate reparative bridge formation for a biological seal.
In addition to sealing the pulp cavity to prevent ingress from bacteria, it is also important to stimulate reparative bridge formation as quickly as possible. Accordingly, pulp capping compositions are preferred which can also stimulate dentin repair when a pulp exposure or near pulp exposure occurs. To increase the likelihood of reparative bridge formation, calcium hydroxide compositions are conventionally utilized. Calcium hydroxide compositions are also used since the high pH of the calcium hydroxide kills bacteria.
Exposure of the pulp often occurs as a result of excavating deep caries in preparation for placing a filling or crown. Restorative dental procedures related to fillings and crowns may require the use of harsh chemicals which can result in postoperative sensitivity if the chemicals contact the pulp. The steps for restorative dental procedures related to fillings and crowns if a deep preparation or exposure has been excavated, generally involve disinfecting the area with a disinfectant, drying the area, placing a pulp cap at or near the opening into the pulp chamber, etching the area, priming the area and then applying a bonding resin for a composite or crown or placing a metal amalgam filling. A properly applied pulp cap not only minimizes the likelihood and degree of postoperative sensitivity from chemicals or bacteria in the dentin tubules near or in the pulp but the postoperative inflammatory response is also reduced; hence healing and predictable nonendodontic success is facilitated.
Although, the survivability of a tooth having an exposed or nearly exposed pulp can be increased by the use of a pulp cap, conventional pulp caps generally fail to adequately seal a treated area and generally have a deleterious impact on the retention of restorations. Any conventional liner has a negative impact on a bonded restoration due primarily to the strength of the liner which is significantly less than that of the covering restorative material.
Glass ionomer cements have been taught as a sealing-type liner. Glass ionomer cements are two components systems comprising a liquid component such as polyacrylic acid and a powder component such as ion leaching glasses, which are mixed together. Unfortunately, calcium hydroxide is not compatible with the polyacrylic acid, as the polyacrylic acid reacts with calcium hydroxide to form a salt, thus inactivating the calcium hydroxide. Glass ionomer cements are also not compatible with disinfectant agents as the agents interfere with bonding. Additionally, glass ionomer cements are significantly weaker than composites or metals. When compared with composites, the strength of the bond adhesion to a tooth is much weaker as the bond can be no stronger than the strength of the weak glass ionomer liner material.
The most significant clinical concern of nonadhesive pulp caps and liners is that strong tooth treatment modality may cause tissue harm. For example, many conventional nonadhesive pulp caps and liners fail to form a seal and those that do form a seal frequently fail due to being dislodged by a dental tool, brush, etc. Additionally, shaping or contouring a composite or metal amalgam filling often causes weak liners to be displaced by the forces experienced during the procedure which yields a liner that is no longer an effective or reliable barrier. As a result, the usefulness of such nonadhesive pulp caps and liners is limited since the protective seal can be compromised by being merely bumped by a dental tool or by being dislodged during instrumented shaping or contouring.
Accordingly, despite the number of materials available to dental practitioners as pulpal protection materials and dentin liners, there is not a known material which provides a highly reliable seal against bacteria ingress and facilitates reparative dentin formation. Conventional liners and pulp caps typically comprise calcium hydroxide liquids formed from at least calcium hydroxide in conjunction with water-based nonpolymerizable materials and polymerizable nonadhesive materials. Examples of conventionally utilized water-based nonpolymerizable materials include calcium hydroxide and water, and usually thickening or gelling materials such as guar gum, xanthan gum, methylcellulose or polycarboxymethylene. The nonpolymerizable materials cause the compositions to be highly viscous and to have low adhesion strengths. Examples of conventionally utilized polymerizable nonadhesive materials include alkyl methacrylates and alkyl amino methacrylates. These polymerizable nonadhesive materials also fail to contribute the properties necessary to provide an effective and reliable seal. These materials are much weaker than the covering restorative materials and hence provide a weak foundation for the stronger definitive restorations.
Accordingly, it would be useful to have dentin liner and pulp capping compositions which provide an effective and reliable seal against ingress from microorganisms, which provide reparative dentin stimulative and which protect an area in a tooth from harsh chemicals used in typical dental restorative procedures.
It would also be useful to have dentin liner and pulp capping compositions which are stable as a one package paste that can be stored and then applied to a dental substrate as needed.
Finally, it would be useful to have dentin liner and pulp capping compositions which have a rheology that enable the compositions to be dispensed from a syringe.